Method of making the arsenate of calcium and analogous elements



' cake delivered to the furnace for oxidation.

to calcium arsenate 1s rapi when the material is brought to a tempera Patented Apr. 7, i925.

Uhllllfldfi JOSEPH F. GULLEN,

REFINING & MINING 0F MIDVALE, "UTAH, ASSIGNOR TO UNITED STATES SMELTING, COMPANY, OF PORTLAND, MAINE, A CORPORATIQN OF MAINE EEETHOD OF MAKING THE ARS ENATE OF CALCIUM AND ANALOGO'O'SELEMENTS. I

Elo lil'awing. Original ap plication filed October 15, 1919, Serial No. 380,910. Divided and this application filed Februarym, 1925.

To all whom it may concern:

lde it known that l,

State of Utah,

and useful Improvements in Making the Arsenate of JOSEPH F. Gunman, States, residing at Salt Lake and Methods of Calcium and Analogous Elements; and I do hereby declare the following to be a full,

scription of the invention,

able others skilled vin appertains to make clear, and exact desuch as will enthe art to which it and use the same.

The invention relates to the manufacture of the arsena-te or arsenates of calcium or analogous elements, such as magnesium, or

of mixtures of such arsenates which are suitable for use as 1nsect1c1des and more particularly to arsenates based on the the manufacture of such for dry dust-- making such discovery that they may be commercially produced by the air oxidation of a mixture of arsenic 'trioxide (white arsenic) and the oxide or hydroxide Tn the further expla tion reference will be procedure applied to calcium arsenate ture of lime and calcium or magnesium or such oxides or hydroxides.

mixtures of nation of the invenmade to a mode of the manufacture of by the oxidation of a mixarsenic trioxide, as indicated in the following equation:

ln accordance with this mode 1 cmre, burned lime 1s disintegrate of proced to a fine powder by slaking with water and is thoroughly oxide.

mixed with powdered arsenic tri- Sufiicient water may be used to 'facilitate the intimate mixing of the ingredients as a thin mud.

After being allowed to stand for a short time the mud stificns and can be shovelled into a reverberatory or may be removed by filtering and the filter The oxidation turc approximating a white arsenic employe complished without ser ous volatilization. The weights of the lime an red heat, and is acloss of arsenic by d may be varied to M ih,

f ticide spray may (1 lime to the furnace pro Serial No. 8,678.

roduce the difierent 'arsenates, viz: so.- called neutral, nates and mixtures of them. a

The changes which take place during the conversion of the lime and white arsenic to calcium arsenate may be further explained as follows. The lime and arsenic trioxide combine and form calcium arsenite when mixed with water. The composition of the arsenite will depend upon the proportion in which the ingredients are employed. If used in the proportion of 3 molecules of lime to 1 molecule of arsenic trioxide, the resulting arsenite will have the composition, Ca (AsO and will be oxidized in the furnace to tricalcium orthoarsenate, CaAAsOQ If used in the ratio of 2 molecules of lime and 1 molecule of arsenic trioxide an arsenite of the approximate composition Ga H AS 0 will re-' sult, which will Pure anhydrous tri-calcium orthoarsenate, contains approximately 57.8

calcium pyro-arsenate, Ca. AS contains approximately 67.2 per cent arsenic pentoxide. Both of these compounds are appreciably soluble in water and, for this reason, their direct use as insecticide sprays is not desirable. By employing larger quantities of lime in proportion to white arsenic, more basic arsenates are obtained which possess little or no solubility in water. alcium arsenateintended for use as an inseche made to contain aproximately 40 per cent arsenic pantoxide. Such regulation or control of the character of the calcium arsenate and of its solubility d in water can be regulated in this process by either the initial adjustment of the weights of lime and arsenic trioxide or preferably by subsequent addition of lime or hydrated duct.

"F or example, lime and arsenic trioxide acid and basic arsemay be initially mixed in the proportion to yield a calcium aisenate of the approximate composition, per cent AS205 and per cent CaO, or the lime and arsenic trioxide may be initially mixed to yield calcium pyro-arsenate and this product subse quently mixed With lime or hydrated lime to yield the product having little or no solubihty in Water and of the approximate coniosition, l0 per cent AS205 and 60 per cent a0.

As heretci 'one indicated the invention may be employed in like manner for the manufacture of dolomitic arsenates and magnesium arsenates by substituting magnesium lime or magnesia for the calcium lime.

The term hydroxide-forming used in the claims is intended to include both the oxide and hydroxide.

This application is a division of application Serial No. 330.910 filed @ctobei? 15, 1919.

While it is preferred to practice the'in vention in the manner it will be describ o. understood that this 15 not essen' el and that the specific mode of rocedurc may be Variously modified or changed without depart-- ing therefrom.

What is claimed is:

l. The method of making arsenate or an ct alkali-earth metals which consists in aii" oxidation at high temperature of mixture of arsenic tiioxide a sut licient quantity of a hydroxide-forming compound of such metals to combine with the arsenic trioztide to form aisenites Which unite. with the oxygen of the arsenates Without material volatilization of arsenic.

2. The method of makingarsenate on at senates of alkali-earth metals which consists in the oxidation at high temperatures of arsenic trioxide and a. hydroxide-forming compound of such metals mixed in substantially the proportions of their combining Weights.

3. The method of making insecticide arsenate oi" arsenat-es of alkali-earth metals which consists in oxidation at high temperature of a mixture of arsenic trioxide and a hydroxide-forming compound of such metale, and reducing the water solubility oi the product by subsequent addition of said hy dioxide-forming compound.

l. The method of making insecticide arsenate or arsenates of alkali-earth metals which consists in the oxidation at high temperature of arsenic trioxide a hydtoitide-fo'rming compound of such metals mixed in substantially the prop their combining weights, and DBClLT water solubility by additional forming compound.

5. The method of manutactui'in i; cide calcium ersenate which cons-i cs1 dation a high temperature of arsenic i??- and lime mixed in proportions to i oasses-sates cont-amin comparatively high pencentsges of oacid preciably soluble in Water,

n anand by subsequent tteetment reducing the w t i bility and the percentage {meme acid in the product. 

